The present invention relates generally to a poly-V pulley formed with a plurality of narrow, deep, V-shaped grooves. The invention further relates to an improved method for manufacturing a poly-V pulley.
Nolte V. Sproul U.S. Pat. No. 3,977,264 discloses a Method of Making Poly-V Pulleys and Product. The poly-V pulley is made by forming a cup-shaped blank with a generally cylindrical annular flange which terminates at its open end in an outturned radial flange. A series of wide opening, shallow, corrugation-like V-shaped grooves then is cold rolled in the cylindrical flange by outwardly and inwardly displacing portions of the flange wall to form rounded groove valleys with intervening round crests, and slightly thinning the flange wall metal in the crests and valleys while presenting appreciable groove side wall thinning. The groove walls then are axially squeezed to compress the walls to sinuous shape while maintaining constant the radial dimensions of the inner and outer rounded surface of the grooves during axial squeezing. The sinuous formed flange wall then is roller worked compressed and extruded to form sharp V-shaped outer groove crests and thickened metal in the groove valley walls.
In the disclosed poly-V pulley, the weight balance on opposite sides of the pulley is not good enough to provide good dynamic balance while rotating. Due to the inadequate dynamic balance, the radius of the flange wall may deviate or excess vibration occurring in the pulley may cause distortion during rotation. This tends to shorten the life not only of the pulley per se but also of the belt due to the uneven distribution of friction on the belt caused by the deflection or distortion of the pulley.
In the disclosed process, since the blank has to be pre-machined or pre-prepared into a cup-shape with the generally cylindrical flange by a deep-drawing process, it has been considered difficult to make a poly-V pulley with a relatively small diameter.